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[Ada] Fix spurious -Wuninitialized warnings for small records

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This change is aimed at getting rid of spurious -Wuninitialized warnings
issued for small records passed by copy and containing default values
for some of their components.

The source of the problem is that the _Init parameter of the
initialization routine is declared as an in/out parameter, so the
uninitialized object is passed by copy to it and this can be flagged by
-Wuninitialized.

That's why the mode of the parameter is changed to out, except for the
cases where information really needs to be passed in: unconstrained
array types, protected and task types.

For the following record type Rec!

 type Rec is record
    B : Boolean := True;
  end record;

the initialization routine must now be:

      procedure r__recIP (_init : out r__rec1) is
      begin
         _init.b := true;
         return;
      end r__recIP;

2018-10-09  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* exp_ch3.adb (Is_Null_Statement_List): New predicate.
	(Build_Array_Init_Proc): Use it to find out whether the
	initialization procedure Is_Null_Init_Proc; if so, set
	Warnings_Off on the parameter.
	(Build_Init_Procedure): Likewise.
	(Init_Formals): Use an in/out first parameter only for
	unconstrained arrays and for records either containing or built
	for proteced types or task types; use an out parameter in all
	the other cases.
	* fe.h (Is_Init_Proc): Declare.
	* gcc-interface/decl.c (type_requires_init_of_formal): Do not
	return true for a discriminant in an unchecked union.
	(gnat_to_gnu_param): Do not create a PARM_DECL for the Out
	parameter of an initialization procedure.

From-SVN: r264984
This commit is contained in:
Eric Botcazou 2018-10-09 15:06:55 +00:00 committed by Pierre-Marie de Rodat
parent 4b9e1bc781
commit c743425fce
4 changed files with 99 additions and 28 deletions
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17
gcc/ada/ChangeLog
View File

@ -1,3 +1,20 @@
2018-10-09 Eric Botcazou <ebotcazou@adacore.com>
* exp_ch3.adb (Is_Null_Statement_List): New predicate.
(Build_Array_Init_Proc): Use it to find out whether the
initialization procedure Is_Null_Init_Proc; if so, set
Warnings_Off on the parameter.
(Build_Init_Procedure): Likewise.
(Init_Formals): Use an in/out first parameter only for
unconstrained arrays and for records either containing or built
for proteced types or task types; use an out parameter in all
the other cases.
* fe.h (Is_Init_Proc): Declare.
* gcc-interface/decl.c (type_requires_init_of_formal): Do not
return true for a discriminant in an unchecked union.
(gnat_to_gnu_param): Do not create a PARM_DECL for the Out
parameter of an initialization procedure.
2018-10-09 Eric Botcazou <ebotcazou@adacore.com>
* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Constant>: If

95
gcc/ada/exp_ch3.adb
View File

@ -202,6 +202,11 @@ package body Exp_Ch3 is
-- Check if E is defined in the RTL (in a child of Ada or System). Used
-- to avoid to bring in the overhead of _Input, _Output for tagged types.
function Is_Null_Statement_List (Stmts : List_Id) return Boolean;
-- Returns true if Stmts is made of null statements only, possibly wrapped
-- in a case statement, recursively. This latter pattern may occur for the
-- initialization procedure of an unchecked union.
function Is_User_Defined_Equality (Prim : Node_Id) return Boolean;
-- Returns true if Prim is a user defined equality function
@ -529,6 +534,7 @@ package body Exp_Ch3 is
Has_Default_Init : Boolean;
Index_List : List_Id;
Loc : Source_Ptr;
Parameters : List_Id;
Proc_Id : Entity_Id;
function Init_Component return List_Id;
@ -722,13 +728,14 @@ package body Exp_Ch3 is
end if;
Body_Stmts := Init_One_Dimension (1);
Parameters := Init_Formals (A_Type);
Discard_Node (
Make_Subprogram_Body (Loc,
Specification =>
Make_Procedure_Specification (Loc,
Defining_Unit_Name => Proc_Id,
Parameter_Specifications => Init_Formals (A_Type)),
Parameter_Specifications => Parameters),
Declarations => New_List,
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
@ -753,18 +760,14 @@ package body Exp_Ch3 is
-- where we have to generate a null procedure in case it is called
-- by a client with Initialize_Scalars set). Such procedures have
-- to be generated, but do not have to be called, so we mark them
-- as null to suppress the call.
-- as null to suppress the call. Kill also warnings for the _Init
-- out parameter, which is left entirely uninitialized.
Set_Init_Proc (A_Type, Proc_Id);
if List_Length (Body_Stmts) = 1
-- We must skip SCIL nodes because they may have been added to this
-- list by Insert_Actions.
and then Nkind (First_Non_SCIL_Node (Body_Stmts)) = N_Null_Statement
then
if Is_Null_Statement_List (Body_Stmts) then
Set_Is_Null_Init_Proc (Proc_Id);
Set_Warnings_Off (Defining_Identifier (First (Parameters)));
else
-- Try to build a static aggregate to statically initialize
@ -2803,18 +2806,14 @@ package body Exp_Ch3 is
-- where we have to generate a null procedure in case it is called
-- by a client with Initialize_Scalars set). Such procedures have
-- to be generated, but do not have to be called, so we mark them
-- as null to suppress the call.
-- as null to suppress the call. Kill also warnings for the _Init
-- out parameter, which is left entirely uninitialized.
Set_Init_Proc (Rec_Type, Proc_Id);
if List_Length (Body_Stmts) = 1
-- We must skip SCIL nodes because they may have been added to this
-- list by Insert_Actions.
and then Nkind (First_Non_SCIL_Node (Body_Stmts)) = N_Null_Statement
then
if Is_Null_Statement_List (Body_Stmts) then
Set_Is_Null_Init_Proc (Proc_Id);
Set_Warnings_Off (Defining_Identifier (First (Parameters)));
end if;
end Build_Init_Procedure;
@ -8612,19 +8611,30 @@ package body Exp_Ch3 is
------------------
function Init_Formals (Typ : Entity_Id) return List_Id is
Unc_Arr : constant Boolean :=
Is_Array_Type (Typ) and then not Is_Constrained (Typ);
With_Prot : constant Boolean :=
Has_Protected (Typ)
or else (Is_Record_Type (Typ)
and then Is_Protected_Record_Type (Typ));
With_Task : constant Boolean :=
Has_Task (Typ)
or else (Is_Record_Type (Typ)
and then Is_Task_Record_Type (Typ));
Loc : constant Source_Ptr := Sloc (Typ);
Formals : List_Id;
begin
-- First parameter is always _Init : in out typ. Note that we need this
-- to be in/out because in the case of the task record value, there
-- are default record fields (_Priority, _Size, -Task_Info) that may
-- be referenced in the generated initialization routine.
-- The first parameter is always _Init : [in] out Typ. Note that we need
-- it to be in/out in the case of an unconstrained array, because of the
-- need to have the bounds, and in the case of protected or task record
-- value, because there are default record fields that may be referenced
-- in the generated initialization routine.
Formals := New_List (
Make_Parameter_Specification (Loc,
Defining_Identifier => Make_Defining_Identifier (Loc, Name_uInit),
In_Present => True,
In_Present => Unc_Arr or else With_Prot or else With_Task,
Out_Present => True,
Parameter_Type => New_Occurrence_Of (Typ, Loc)));
@ -8632,9 +8642,7 @@ package body Exp_Ch3 is
-- formals, _Master : Master_Id and _Chain : in out Activation_Chain
-- We also add these parameters for the task record type case.
if Has_Task (Typ)
or else (Is_Record_Type (Typ) and then Is_Task_Record_Type (Typ))
then
if With_Task then
Append_To (Formals,
Make_Parameter_Specification (Loc,
Defining_Identifier =>
@ -9022,6 +9030,43 @@ package body Exp_Ch3 is
end loop;
end Init_Secondary_Tags;
----------------------------
-- Is_Null_Statement_List --
----------------------------
function Is_Null_Statement_List (Stmts : List_Id) return Boolean is
Stmt : Node_Id;
begin
-- We must skip SCIL nodes because they may have been added to the
-- list by Insert_Actions.
Stmt := First_Non_SCIL_Node (Stmts);
while Present (Stmt) loop
if Nkind (Stmt) = N_Case_Statement then
declare
Alt : Node_Id;
begin
Alt := First (Alternatives (Stmt));
while Present (Alt) loop
if not Is_Null_Statement_List (Statements (Alt)) then
return False;
end if;
Next (Alt);
end loop;
end;
elsif Nkind (Stmt) /= N_Null_Statement then
return False;
end if;
Stmt := Next_Non_SCIL_Node (Stmt);
end loop;
return True;
end Is_Null_Statement_List;
------------------------------
-- Is_User_Defined_Equality --
------------------------------

6
gcc/ada/fe.h
View File

@ -156,6 +156,12 @@ extern void Setup_Asm_Outputs (Node_Id);
extern void Get_Encoded_Name (Entity_Id);
extern void Get_External_Name (Entity_Id, Boolean, String_Pointer);
/* exp_tss: */
#define Is_Init_Proc exp_tss__is_init_proc
extern Boolean Is_Init_Proc (Entity_Id);
/* exp_util: */
#define Is_Fully_Repped_Tagged_Type exp_util__is_fully_repped_tagged_type

9
gcc/ada/gcc-interface/decl.c
View File

@ -5153,7 +5153,7 @@ type_requires_init_of_formal (Entity_Id type)
Present (field);
field = Next_Entity (field))
{
if (Ekind (field) == E_Discriminant)
if (Ekind (field) == E_Discriminant && !Is_Unchecked_Union (type))
return true;
if (Ekind (field) == E_Component
@ -5334,11 +5334,14 @@ gnat_to_gnu_param (Entity_Id gnat_param, tree gnu_param_type, bool first,
type doesn't require the initialization of formals, we don't make a
PARM_DECL for it. Instead, it will be a VAR_DECL created when we
process the procedure, so just return its type here. Likewise for
the special parameter of a valued procedure, never pass it in. */
the _Init parameter of an initialization procedure or the special
parameter of a valued procedure, never pass them in. */
if (Ekind (gnat_param) == E_Out_Parameter
&& !by_ref
&& !by_component_ptr
&& (!type_requires_init_of_formal (Etype (gnat_param)) || by_return))
&& (!type_requires_init_of_formal (Etype (gnat_param))
|| Is_Init_Proc (gnat_subprog)
|| by_return))
return gnu_param_type;
gnu_param = create_param_decl (gnu_param_name, gnu_param_type);